1. Field of the Invention
The present invention relates to a fluid dynamic bearing device. This fluid dynamic bearing is suitable as a bearing device for use in a spindle motor for an information apparatus, for example, a magnetic disk apparatus, such as an HDD or an FDD, an optical disk apparatus, such as a CD-ROM, a CD-R/RW, or a DVD-ROM/RAM, or a magneto-optical disk apparatus, such as an MD or an MO, a polygon scanner motor for a laser beam printer (LBP), a color wheel motor for a projector, or a small motor for an electric apparatus, such as an axial flow fan.
2. Description of the Related Art
Apart from high rotational accuracy, an improvement in speed, a reduction in cost, a reduction in noise, etc. are required of the various motors mentioned above. One of the factors determining such requisite performances is a bearing supporting a spindle of the motor. Recently, as a bearing of this type, use of a fluid dynamic bearing superior in the above-mentioned requisite performances is being considered, or such the fluid dynamic bearing has been actually put into practical use.
JP 2000-291648 A discloses, as an example, a fluid dynamic bearing device which is to be used in a spindle motor for a disk drive device, such as an HDD. In the bearing device, a bearing sleeve is fixed to an inner periphery of a housing in a form of a bottomed cylinder, and a shaft member having an outwardly protruding flange portion is inserted into an inner periphery of the bearing sleeve. A fluid dynamic pressure is generated in a radial bearing gap and a thrust bearing gap formed between the rotating shaft member and stationary members (i.e., the bearing sleeve, the housing, etc.), and the shaft member is supported in a non-contact fashion by this fluid dynamic pressure.
The fluid dynamic bearing is composed of components, such as a housing, a bearing sleeve, a shaft member, a thrust member, and a seal member. To secure the high bearing performance required as performance of information apparatuses becomes increasingly high, efforts are being made to achieve an improvement in machining precision and assembly precision for the components. On the other hand, with a tendency of information apparatuses toward a reduction in price, a demand for a reduction in cost of such the fluid dynamic bearing device is becoming increasingly strict.